I realize that this type of query is rather rare. But it's not entirely impossible. What is leaving me puzzled: There is a patch for this ready since september, seeing very little love. So what is keeping this bug from being fixed?

programmer /ˈprəʊgramə/, noun: a device that converts ►coffee into ►code

Yes, this bug exists also in the 1.1.8 version.
The problem is in the CDbCommandBuilder::createUpdateCounterCommand().
It builds the update and only after then calls the applyjoin() function, which simply appends the join part.